1. Field of the Invention
The present invention relates to multilayer ceramic electronic components, and, in particular, to a multilayer ceramic electronic component including stacked ferrite ceramic layers.
2. Description of the Related Art
Ferrite ceramic materials are often used to form main bodies defining inductor components. Usually, conductive films used for terminals or portions of coil conductors are arranged on a surface of a main body. The conductive films are, for example, thick films formed by applying a conductive paste including silver and baking the paste. Such conductive films that are made of the thick films including silver, in particular, the conductive films defining terminals often cause a problem of solder leaching when bonded to a circuit board by soldering. Thus, the conductive films including silver are usually subjected to nickel plating. Furthermore, to improve solderability, tin, solder, or gold plating is performed.
The nickel plating and tin plating are performed by electroplating. However, the following problem may arise when performing the electroplating.
The ferrite ceramic material defining the main body of the inductor component typically has a relatively low resistivity as compared to, for example, insulating ceramic materials. Thus, the anomalous deposition of plating films, in which the plating films are deposited on the conductive film and a surface of the main body other than the conductive film, may occur when the electroplating is performed. The anomalous deposition of the plating films leads to, for example, a reduction in the distance between the terminals made of the conductive films. In particular, for small-sized inductor components, this may cause a reduction in withstand voltage and, in the worst case, a short-circuit failure.
The related art is described in Japanese Unexamined Patent Application Publication No. 2003-272914. Patent Application Publication No. 2003-272914 describes a multilayer inductor component including a main body having a multilayer structure made of a ferrite ceramic material to which bismuth is added as a sintering agent. The addition of bismuth as a sintering agent permits the ferrite ceramic material to be sintered at a lower temperature. Therefore, internal conductors made of silver can be used.
However, for the multilayer inductor component as described in Patent Application Publication No. 2003-272914, when the conductive films arranged on the outer surfaces of the main body are subjected to electroplating, the foregoing anomalous deposition of the plating films occurs more readily. The anomalous deposition was determined to be attributed to the bismuth. It was determined that bismuth was present in the form of Bi2O3 at boundaries of the ferrite ceramic material and the anomalous deposition of the plating films typically occurred at the boundaries at which bismuth was present on the surfaces of the main body.